Sheets of waterproof membranes made of rubber or plastic have been used for several years to line ponds and to cover the water in some water reservoirs. The use of similar sheets of material have been used in roofing systems, particularly structures having large roof areas. The membranes have been attached to the roof structure by adhesives covering the entire membrane or other systems adhere the membrane only to selected spot connections. When the entire membrane is adhered to the roof structure, normal expansion and construction in the roof sets up stresses in the membrane which ultimately results in failure along the stress lines. Where the membrane is attached at localized areas, stress is caused at the localized areas due to the wind lifting and shifting the membrane with respect to the roof.
Others have secured the membrane to the roof by placing weighting materials on top of the membrane such as a layer of gravel. While this system satisfactorily holds the membrane to the roof, the weighting materials adds considerable weight to the structure which requires that all structural elements be stronger thereby adding to the cost of the structure.